Vessel with vertically elevational support legs

ABSTRACT

A vessel, preferably a chip, for transport and mounting of structures has a hull and at least four vertically elevated support legs and displacement apparatus for elevating the support legs so as to stabilize the ship for lifting heavy loads from the ship for mounting for example to a preinstalled base on the seabed.

BACKGROUND

The invention relates to a vessel, preferably a ship, for transport andmounting of structures, said vessel comprising a hull and at least fourvertically elevational support legs as well as displacement means forelevating the support legs.

Such a vessel is known from for instance GB-A-2,120,607. In thisspecification a ship is described which is used for installation oflarge offshore structures. The ship is equipped with four elevationallymovable legs and a rail device on the deck of the ship. However, theship is specially designed in the sense that the four elevationalsupport legs form an integral part of the vessel and accordingly aremounted through its deck. Moreover, use of the rail structure means thatthe ship can only be used when a structure is extended outward from thedeck and is to be arranged on a platform on a level with the deck'ssurface.

In connection with the mounting of windmills offshore it is furthermoreknown to transport same on a jack-up barge, which is towed out or whichmay perhaps sail on its own, and where only one mill at a time can becarried along, and where the speed of the transport unit is verylimited. Such a jack-up is also very sensitive to wind conditions, forwhich reason it is only possible to erect the mills partly relativelydose to land and partly in relatively calm weather.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a vessel which basedon an existing vessel, i.e. complete with all gear, makes it possible totransport windmills and mount these mills on previously built structureson the seabed, and where the windmill erection itself will take placeunder the same conditions on land, and where the mounting may take placevia cargo ships of the self-supplying type. The ship is in other words aunit which can handle all tasks comprising loading of the mill units,transport of several mill units to the mounting site, including liftingthereof from the cargo ship and lowering thereof to the preinstalledbase on the seabed.

The ship is accordingly a cargo ship, preferably a container ship or abulk carrier, to which certain structural additions have been made. Thecargo ship distinguishes itself by holding a big cargo, which in thiscase will be up to 10 windmills, but at the same time also being highlyseaworthy and able to maintain good speed, just as such a cargo shipholds the necessary facilities for the crew.

The object of the invention is achieved by a vessel of the typedescribed in the preamble and where the support legs are furthermoremounted in at least two consoles which by first means are connected tothe hull's right and left long side, respectively, and where the vesselalso comprises at least one auxiliary structure, preferably a crane, forhandling and placing the structures below the waterline.

The system accordingly functions by securing the mentioned consoles toknow vessels by means of first mans which for example may be a raildevice. Through each console there is mounted one preferably twoelevationally movable legs, said legs ensuring that the ship will remainstationary, even in rough sea. It should be noted that in connectionwith the handling of the windmills a locking of the legs will take placein that the ship is raised to the necessary level, whereupon a blockingtakes place since a high wave would otherwise give rise to instabilityduring handling of the mills. By means of the crane itself it is thuspossible to handle the large windmills, and where on the deck there mayfurthermore be mounted additional auxiliary cranes to ensure loading toand from the quay.

By providing a vessel according to the invention, the support legs willslide relatively frictionless in the sleeve which partially encloses thesupport legs. The sleeve may as disclosed be coated with a frictionreducing substance, preferably in the form of teflon, or the supportlegs may be coated with teflon for achieving the same function.Furthermore, the legs are adapted for the sleeve via a sliding fit sinceit is important that there is not too much clearance between sleeve andsupport leg.

By providing a vessel according to the invention, an appropriate methodfor adjusting the vertical position of the support legs is achieved,since the hydraulic system will provide for the correct pressure on thesupport legs. It should also be noted that each support leg preferablyhas two wire winches mounted on either side thereof. The number ofwindings on the wire winch indicates that gear ratio where a gear of 9is preferably preferred in such a manner that when the wire winchproduces a 35 ton load, the pressure which is produced via a hydraulicstation on each support leg may reach up to approximately 300 tons.

By providing a vessel according to the invention, the pressure on eachindividual support leg may be measured and indicated via the load cell.

By providing a vessel according to the invention, it is possible toadjust the weight in such a manner that when a corner exerts a highpressure on the load cells, such as disclosed in claim 4, they will senda message to the control system to change the pressure diagonallyopposite this unit. This is accomplished by removing liquid from thechambers in this corner and by pumping in liquid in the diagonallyopposite corner, thus achieving a form of equilibrium and compensatingfor the load weight that is moved. This anti-heeling system may beactive both when the ship is floating and when it is anchored on theseabed via the support legs. In the first instance, a liquid sensor andgyro function will register heelings of the ship and a signal istransmitted from the sensor to the anti-heeling system, thus ensuringthe stability of the ship.

In the latter instance, where the liquid sensors are not functioning,the load cells mounted on the support legs will register any pressureand any change of pressure on the support legs, when a load is moved,and will signal this information to the anti-heeling system, which isthus activated and compensates for the differences in pressure.

By providing a vessel according to the invention, an appropriate size ofthe console itself is achieved such that good control of the supportlegs within the longitudinal sleeve is achieved, said sleeve beinglocated inside the console, or which is obtained by means of the holeswhich are cut in the upper and lower surfaces of the console to providean aperture through the support legs may slide.

By providing a vessel according to the invention, the console will makeup a removable unit which thus an be dismounted from/mounted on thestructures of the known vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further explained below with reference to thedrawing wherein

FIG. 1 is a top sectional view of a ship with tank/consoles mountedthereon with support legs and mounted cranes,

FIG. 2 is a cross section of a crane mounted on a ship,

FIG. 3 is the position of the support leg in relation to thetank/console and the winch therefore,

FIG. 4 is a top view of the tank/console with winch and support legshown in FIG. 3,

FIG. 5 is a cross section through the tank with support leg mounted onthe side of the ship,

FIGS. 6A-C is the interaction of wire winch and support leg.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a top view of a ship 1, comprising a hull 2, a deck 3, uponwhich deck two smaller auxiliary cranes 10 are positioned. On eitherside of the hull there is mounted a console 5, in which support legs 9are placed, preferably two support legs at either end of the console.The support legs are on either side connected to a winch with wire 8,said wire winch providing for the right pressure on the support legs 9via a hydraulic system.

The columns of the support legs are rectangular and end in a base in theorder of 10 m² and are furthermore manufactured according to knownprinciples.

The base itself is in the form of a plate and is arranged in a cardanicsuspension such that its inclination adjusts to the slope of the seabed.The area of the support bases may be extended since they are detachablymounted on the support legs.

Between each pair positioned opposite each other on either side of thehull a large crane 11 is positioned, said crane being capable of liftingand mounting windmills to a previously mounted base on the seabed.

Furthermore, the ship comprises additional cranes 10, since cargo shipsare known to have smaller cranes which are positioned at either end ofthe ship, which cranes can be used for ordinary loading, and which may,if required, be used during the lowering of the mill itself, since theseact as guides for the mill wings.

The ship comprises a large crane which has a loading capacity of about450 tons. This crane is taken from known, so-called caterpillar craneswhere the movable part is removed, and the crane is accordingly mountedstationarily on the ship's deck, in that the crane is positioned in themiddle of the longitudinal direction of the ship, preferably halfwaybetween two support legs positioned opposite each other and on eitherside of the hull, but displaced or displaceable, however, to one or theother side of the longitudinal side of the ship. On the ship there ismounted a 12 meter tower on which the crane is positioned, whereby thecrane reaches a height which makes it possible to handle the extremelyhigh windmills.

FIG. 2 shows a side view of the crane 11, from which it appears thatsame is displaced towards one of the long sides of the ship. FIG. 2 alsoshows pockets in the sides of the hull itself, said pockets 12 formingpart of the anti-heeling system, and which can also be coupled with thefunctioning of the large crane 11. The anti-heeling system is primarilybuilt in to bring about a counterbalance to the moment of the smallercranes during operation in that these chambers, which the anti-heelingsystems normally cooperate with, are filled with water diagonallyopposite the side wherein a crane is working so that the ship does nottip. This anti-heeling system has thus in a novel manner becomeactivated in connection with the use of the large crane in that acontrol system has been built in, said control system being connected toload cells placed on the support legs and, if desired, at each supportbase, and said load cells registering changes in the pressure on theindividual leg. In the cases where a load cell for example indicatespressure on a leg of around 350 tons and changed e.g. from 200 tons, theload cell will send a message to the control system regarding a changediagonally opposite this unit by removing liquid in the 350 tons cornerfrom the anti-heeling system and by pumping in liquid in the diagonallyopposite corner so that a form of equilibrium is achieved.

The system may be controlled via a computer program, or it may behandled purely manually. It should be noted that the ship with thebuilt-in support legs and crane is designed to be capable of operatingin a 3 meter actual wave height, which corresponds to 1½ meterssignificant wave, since it is essential by the structure that it can beheld plane under the forces existing by such a wave condition. Whatdecides whether or not it is possible to erect a mill will therefore notbe the sea conditions, but on the contrary the actual wind conditions,and said wind conditions will be the same as are existing on land.

In the cases where an actual wave height is in excess of 3 m, thepressure on a support leg will be in excess of 300 tons, so that thesupport leg with the actual dimensions cannot be held stable. Thesupport leg can naturally by giving the wire winch more windings achievea higher pressure effect, but this is not relevant since a heavier seawill imply a higher wind force, and where this wind force is so highthat the windmill cannot be positioned, since in that case the wind willexert too great a pressure on the wings of the windmill itself.

Furthermore, the structure comprises load cells 13 which are attached toeach support leg 9, in that each support leg 9 also extends within asleeve 14 and is coated with teflon to create less friction resistance.

FIG. 3 is a side view of the tank/console 5 and through which a supportleg, preferably two, are positioned, in that at least one, preferablytwo, wire winches 8 are attached to each support leg. This isfurthermore seen in FIG. 4, from which it is apparent that the console 5encloses the support legs 9 within their sleeve 14, and where thementioned winches 8 are arranged on either side, whereas FIG. 5 shows across section through the console 5, said console being removablymounted to the hull 2, in that to the hull's long sides there is weldeda longitudinal rail 6, which is L- to V-shaped, and into the recess ofwhich a plate portion from the tank rests and where the top end of thetank via a bolt is mounted on the cargo ship. Through this tank/console5 the support leg 9 is accordingly positioned. The tank ends at the topon a level with the deck/rail, whereas the lower portion issubstantially below the water line. During the mounting of a windmillthe ship will thus on all four legs exert a pressure of 300 tons, whichwill lift up the ship, whereafter the winch is locked such that apossible wave will not give rise to instability. If the winch is notlocked, a pressure equalisation will take place via the functionattached to each leg so that the instability is neutralised. Each leghas a length of approximately 20 m.

Mounting of the consoles takes place by a bolted joint which is put inthe hull by each so-called web frame, with a bolt on either side.

The hollow space between the hull and the consoles on the slantedsurface immediately below deck level is treated with Chockfast, a highlyadhesive friction substance, which thus transfers forces from supportlegs and consoles to the hull over a significantly larger carryingsurface than by exclusively using a bolted joint where only the stressresultant of the bolted joint can be taken into account.

The rail connection itself at the base of the consoles is provided tohold the consoles in the correct position the whole time and functionstherefore only as a hinge in that it prevents the consoles from tippingout from the hull. Accordingly, it does not carry the ship at all.

By the above described product the ship will be lifted out of the waterto such an extent that waves up to a certain size will have no influenceon the ship.

All other systems lift the floating object all the way out of the waterwith the drawbacks associated therewith, in that those systems,so-called jack-ups, are highly sensitive at the moment when the bottomof the object just leaves or meets the surface of the sea, if there arewaves, so that it can take long time between removal from oneoperational place to another, in this case from mill to mill, whereoferection of 50 mills may well be planned.

FIG. 6A shows how a wire winch presses the leg against the bottom, oneend of the wire being fastened to the support leg, and the other endbeing mounted on a hydraulic winch with automatic tightening (tension),which is normally used for mooring winches on larger ships.

When the ship is at the position, the legs are lowered to the bottom ofthe sea, and the ship is lifted so much that it is not moving. Then thewinches are set to tension so that the ship may follow the rising andfalling tide. Sufficient lift will normally be at about 5% of the ship'sdisplacement. When the accurate mounting itself is to be made, the legsare locked and the pressure of the legs controlled by the trim system ofthe ship such that the heeling moment from the load hanging in the craneis equalized by ballast water, which is moved in the opposite direction.

When practically applied, the anti-heeling system is put out of actionat the moment when the support legs are put down. This happens becausethe system functions by means of impulses from the ship's heelingsensors in such a manner that it will compensate by working opposite thesignals thereof, but since the ship does not heel, the system will notreceive any signals.

The load cells register the change in pressure which is stored in acontrol panel. The operator or the administrative control systemcontinuously controls the pressure on each of the 4 legs and thusdecides if there is to be a redistribution of the ballast of the ship.

These sensors are bypassed by mounting load cells on each support leg.Via an Ethernet connection—since the load cell gives an electric signalsimilarly to said sensors—the anti-heeling system of the ship may againreceive impulses corresponding to those given by the heeling sensors. Inthis way, the anti-heeling system may be manipulated into thinking thatthe ship is heeling, which is clearly not the case, and will thereforecompensate for the moved load.

In principle, there is no connection between the winches and the loadcells since the winches are mooring winches functioning by giving aconstant hydraulic pressure. If the resistance in the wire declines, thewinch will start to haul in, and vice versa, if the resistance in thewire rises to a level higher than the hydraulic pressure, then the winchwill ease off the wire until the original pressure is established. Thisis brought about by means of a kind of excess pressure valve whichrespectively shuts off and opens for the flow of oil.

FIG. 6B shows how the wire is cut for pressure, but a combination ofwinch size and number of cuttings may be adjusted to any ship.

The drawing, FIG. 6C, shows the lift system where the hydraulic winchalso is likewise a tension winch, but only with the function of holdingthe wire taut in all situations.

What is claimed is:
 1. A ship for transport and mounting of structures,said ship (1) comprising a hull (2) having at least four verticallymovable support legs (9) engaged thereto and displacement means formoving the support legs (9) upward and downward relative to the hull(2), the support legs (9) mounted in at least two consoles (5) fixedlymounted to a right side and a left side of the hull by first means, theship having at least one crane (11), for handling and placing thestructures, the displacement means adjusting the position of the supportlegs (9) for lifting the ship (1) attached thereto to such an extentthat waves up to a certain preselected size do not destabilize the ship(1), during the handling and placing of the structures by the crane,with a bottom of the ship remaining below sea surface.
 2. The shipaccording to claim 1 wherein the consoles (5) comprise at least onesleeve (14) coated with a friction reducing substance on an innersurface thereof, said inner surface enclosing a portion of an outercircumference of a support leg (9).
 3. The ship according to claim 1wherein the displacement means comprise at least one wire winch (8)attached to each of said support legs (9) and a hydraulic systemattached thereto.
 4. The ship according to claim 1 wherein the supportlegs each comprise load cells (13).
 5. The ship according to claim 1further comprising hollow spaces or chambers (12) in the hull (2) and acontrol system, said hollow spaces or chambers being filled with oremptied of water via the control system.
 6. The ship according claim 1wherein an upper end surface of each console (5) is placed on a levelwith a deck (4) of the ship.
 7. The ship according to claim 1 wherein alower end surface of each console (5) is placed at a level distant froma waterline of the ship, between the waterline and a bottom of the ship.8. The ship according to claim 1 wherein in the first means comprise arail secured to the hull and fastening means.